1. Field of the Invention
The present invention relates to a pixel and an organic light emitting display using the same, and more particularly to a pixel capable of compensating for the degradation of an organic light emitting diode, and an organic light emitting display using the same.
2. Description of Related Art
In recent years, there have been many attempts to develop various flat panel displays having a lighter weight and a smaller volume than that that of a cathode ray tube display. The flat panel displays include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting display (OLED), etc.
Amongst the flat panel displays, the organic light emitting display displays an image by using an organic light emitting diode which generates light by utilizing the recombination of electrons and holes. Such an organic light emitting display has an advantage that it has a rapid response time and may be driven with low power consumption.
FIG. 1 is a circuit diagram schematically showing a pixel 4 of a conventional organic light emitting display.
Referring to FIG. 1, the pixel 4 of the conventional organic light emitting display includes an organic light emitting diode (OLED) and a pixel circuit 2 coupled to a data line (Dm) and a scan line (Sn) to control the organic light emitting diode (OLED).
An anode electrode of the organic light emitting diode (OLED) is coupled to the pixel circuit 2, and a cathode electrode is coupled to the second power source (ELVSS). Such an organic light emitting diode (OLED) generates the light with set (or predetermined) luminance to correspond to an electric current supplied from the pixel circuit 2.
The pixel circuit 2 controls an electric current capacity supplied to the organic light emitting diode (OLED) to correspond to a data signal supplied to the data line (Dm) when a scan signal is supplied to the scan line (Sn). For this purpose, the pixel circuit 2 includes a second transistor (M2) coupled between the first power source (ELVDD) and the organic light emitting diode (OLED); a first transistor (M1) coupled between the second transistor (M2), and the data line (Dm) and the scan line (Sn); and a storage capacitor (Cst) coupled between a gate electrode of the second transistor (M2) and a first electrode of the second transistor (M2).
A gate electrode of the first transistor (M1) is coupled to the scan line (Sn), and a first electrode of the first transistor (M1) is coupled to the data line (Dm). And, a second electrode of the first transistor (M1) is coupled to one side terminal of the storage capacitor (Cst). Here, the first electrode of the first transistor (M1) is set to be a source electrode or a drain electrode, and the second electrode is set to be the other electrode that is different from the first electrode. For example, when the first electrode is set to be a source electrode, the second electrode is set to be a drain electrode. The first transistor (M1), coupled to the scan line (Sn) and the data line (Dm), is turned on when a scan signal is supplied to the scan line (Sn), thereby supplying a data signal, supplied from the data line (Dm), to the storage capacitor (Cst). At this time, the storage capacitor (Cst) is charged with a voltage corresponding to the data signal.
The gate electrode of the second transistor (M2) is coupled to one side terminal of the storage capacitor (Cst), and the first electrode of the second transistor (M2) is coupled to the other side terminal of the storage capacitor (Cst) and the first power source (ELVDD). A second electrode of the second transistor (M2) is coupled to an anode electrode of the organic light emitting diode (OLED). Such a second transistor (M2) controls an electric current capacity to correspond to the voltage value stored in the storage capacitor (Cst), the electric current capacity flowing from the first power source (ELVDD) to the second power source (ELVSS) via the organic light emitting diode (OLED). At this time, the organic light emitting diode (OLED) generates light corresponding to the electric current capacity supplied from the second transistor (M2).
However, the above-mentioned organic light emitting display has a problem in that it is difficult to display an image with desired luminance due to the changes in efficiency caused by the degradation (or deterioration) of the organic light emitting diode (OLED). That is, the organic light emitting diode (OLED) degrades with time, and therefore it is difficult to display the image with the desired luminance over time because the organic light emitting diode (OLED) with more degradation generates light with lower luminance than that of an organic light emitting diode (OLED) with less degradation.